DE2838016A1 - METHOD FOR PRODUCING CHLORCYAN - Google Patents

Description

Patent attorneys Dipl.-Ing. H. Ψετλμανν, Bipl.-Phys. Dr. K. Fincke

Dipl.-Jtsg. RA ₁ ¹ WeICKMANk, Dipl.-Chem. B. Huber Dr. Ing.H. Li ska

_HCH 8000 MUNICH 86, THE 3 «fe 1978

POST BOX 860 820 SKW 217 MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

SKW TROSTBERG AKTIENGESELLSCHAFT 8223 Trostberg

Process for the production of cyanogen chloride.

030011/0263

The invention relates to a process for the production of chlorine cyanide from hydrocyanic acid and chlorine in a non-aqueous reaction medium.

Cyanogen chloride is the starting product for the production of cyanuric chloride, that for the ^ production of herbicides, optical Brighteners, dyes etö> »is used on a large scale. According to known processes, cyanogen chloride is usually obtained by introducing hydrocyanic acid and chlorine into aqueous, dilute hydrochloric acid solutions according to the reaction equation

H _? 0
HCN + Cl ₂ —— * CNCl + HCl -;

(Ulimann, Vol. 9, p. 652 (1975)). In a strongly acidic aqueous medium, it depends on the hydrochloric acid concentration Hydrolysis of the cyanogen chloride. The ammonium chloride formed during the hydrolysis can, under certain circumstances, be reacted with the reactant chlorine nitrogen trichloride is formed. To the The economic efficiency of the process cannot be worsened by too high a degree of hydrolysis and the formation of nitrogen trichloride also does largely suppresses the considerable danger posed to the plant and the personnel The hydrochloric acid concentration of the reaction medium is generally kept at 8 to 16% by weight, preferably at 10% by weight. These Procedure leads to a significant seizure vori strong dilute aqueous hydrochloric acid for which the equivalent value contained in the starting material chlorine can no longer be achieved.

A further problem with this procedure is the further use or disposal of the considerable quantities of these dilute hydrochloric acid.

Attempts have therefore been made to develop processes in which the compulsory accumulation of hydrogen chloride is controlled in such a way that it compared to chlorine, none or at most only a slight one

030011/0263

Depreciation represents. This has to that in DE-AS 18 "o1 disclosed process, in which hydrogen cyanide and chlorine in a non-aqueous, polar, the reactants and reaction products to react against inert organic liquid. However, this method only leads to relatively low yields (5 4 to 85%) and thus proves to be at the high acquisition costs for the raw materials uneconomical.

The object of the present invention is to avoid these disadvantages and to create a process which has high yields supplies, results in few by-products and allows hydrogen chloride to accumulate in an easily usable form.

This object was achieved, surprisingly, in that non-aqueous and / or dehydrating inorganic solvents, which in turn do not react with any of the reactants hydrogen cyanide and chlorine, as a reaction medium for the reactants be used.

The process according to the invention for the preparation of cyanogen chloride from hydrogen cyanide and chlorine with formation of hydrogen chloride is therefore characterized in that the reaction is carried out in a non-aqueous and / or dehydrating inorganic solvent or a mixture thereof at temperatures between ⁰ ° C. and the boiling point of the solvent and pressures between 1 and 6 bar.

The invention leads to a practically complete conversion and gives quantitative yields of cyanogen chloride.

As already mentioned, both non-aqueous solvents can be used inorganic solvents as well as dehydrating inorganic solvents that act against the reactants are inert. Phosphorus oxy-

030011/0263

Chloride, sulfuryl chloride and silicon tetrachloride. However, the other inorganic solvents can also be used, if they are inert, the reaction components are able to dissolve and are liquid in a temperature range, in the conversion of chlorine and hydrocyanic acid at a similar rate expires. Mixtures, in particular those of the preferred solvents mentioned, can also be used for the inventive Use procedure. For example, mixtures of 50 to 80% by volume of phosphorus oxychloride and 50 to give 2o vol. ~% Silicon tetrachloride likewise a quantitative conversion.

The process according to the invention can be carried out at normal pressure, but a reaction under excess pressure is from technical Reasons preferred. In many cases, the cyanogen chloride formed is processed directly in a closed system. For this purpose, overpressure is generally preferred. However, the reaction itself also proceeds under normal pressure advantageous as under overpressure.

The process according to the invention can be discontinuous or continuous carried out v / ground, the latter is preferred. The solvent is expediently placed in the reactor and chlorine and Hydrocyanic acid are introduced into the reaction solution either batchwise or continuously in essentially equivalent amounts. The chlorine is preferably introduced in gaseous form, whereas the hydrocyanic acid is preferably introduced at a corresponding rate metered in in liquid form. The desired reaction temperature between O C and the Boiling point of the solvent used, preferably between 3o and 5o ° C, set.

Likewise, the reaction is preferably carried out at pressures from 1 to 2 bar.

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2338016

in order to obtain the desired purity of the cyanogen chloride, the The mixture of cyanogen chloride and hydrogen chloride which is withdrawn from the reactor is expediently combined with one of the reactants in question Coming solvent or solvent mixtures washed and then unreacted hydrocyanic acid and chlorine in the reactor sump returned. The washing is preferably carried out with the same solvent or solvent mixture that is also used as Reaction medium is used. The gaseous mixture of hydrogen chloride and cyanogen chloride that emerges during this gas scrubbing process is then separated in the usual way.

As already mentioned, the method according to the invention leads to quantitative sales. Another particular advantage is that when the reactants are used in equimolar amounts, they are water-free Hydrogen chloride is obtained, which is either used directly for hydrochlorination processes, can be used for chlorine recovery or for the production of concentrated hydrochloric acid.

The following examples illustrate the invention. Example"!

2oo ml of phosphorus oxychloride were placed in a multi-necked round-bottomed flask with an attached wash column. 27 g / h of hydrocyanic acid and 71 g / h of chlorine in each case in equivalent amounts were metered into the solvent. The temperature in the reactor was adjusted to 40 ° C. About 50 ml / h of phosphorus oxychloride were applied to the wash column located above the flask. The gas-analytical examination of the reaction gas showed that if the reactants were metered in exactly, it only consists of hydrogen chloride and cyanogen chloride. The quantitative evaluation yielded a reaction gas composed of 63% by weight of cyanogen chloride and 37% by weight of hydrogen chloride. The conversion to cyanogen chloride was determined to be 100 % .

030011/0263

Example "1 '2

In the experimental apparatus described in Example 1, 3oo ml of sulfuryl chloride were used as the solvent instead of the phosphorus oxychloride under the reaction conditions specified there. The .B & eätt ^ nd & n .. "chlorine" and hydrocyanic acid were metered in at 107 g / h and 41 g / h, respectively. In the case of this solvent, too, a quantitative conversion of the reactants was found with an exact dosage.

Example 3

In the experimental apparatus described in Example 1 were 2oo ml of a mixture of 7o% phosphorus oxychloride and 3o% silicon tetrachloride. Into this solvent jar 142 g / h of chlorine and 54 g / h of hydrocyanic acid were passed in. The temperature in the reactor was adjusted to 40.degree. By throttling of the gas mixture being withdrawn, a pressure of 2 bar was maintained in the reactor. With exact dosing of the reactants quantitative conversion to cyanogen chloride was obtained.

030011/0263

ORIGINAL INSPECTED

Claims (4)

2833016 X claims 1. A process for the preparation of cyanogen chloride from hydrocyanic acid and chlorine with the formation of hydrogen chloride, characterized in that iran carries out the reaction in non-aqueous and / or dehydrating inorganic solvents at temperatures between O ⁰ C and the boiling point of the solvent and pressures of 1 to 6 bar . 2. The method according to claim 1, characterized in that man the rea] performs. the reaction in the temperature range between 3o and 5o ° C 3. The method according to claim 1 or 2, characterized in that nan carries out the reaction at pressures of 1 to 2 bar. 4. The method according to any one of claims 1 to 3, characterized in that the gas mixture withdrawn from the reactor with the same solvent or mixture as the reaction medium is used, washes and recycled hydrocyanic acid and chlorine. 030011/0263 ORIGINAL INSPECTED